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sass-loader
Advanced tools
The sass-loader npm package is a loader for webpack that allows you to preprocess .scss or .sass files to standard CSS. It uses the Sass compiler to convert Sass code into CSS, and then webpack can bundle the resulting CSS into your final build.
Compiling Sass/SCSS to CSS
This webpack configuration snippet demonstrates how to set up sass-loader in conjunction with css-loader and style-loader to process .scss files.
module.exports = {
module: {
rules: [
{
test: /\.scss$/,
use: [
'style-loader',
'css-loader',
'sass-loader'
]
}
]
}
};
Source Maps
This code enables source maps for easier debugging of Sass files. It configures sass-loader to generate source maps so that the browser dev tools can display the original Sass code instead of the compiled CSS.
module.exports = {
module: {
rules: [
{
test: /\.scss$/,
use: [
'style-loader',
{
loader: 'css-loader',
options: { sourceMap: true }
},
{
loader: 'sass-loader',
options: { sourceMap: true }
}
]
}
]
}
};
Custom Functions
This example shows how to add custom functions to the Sass compilation process. The custom 'pow' function can be used within Sass files to compute powers.
const sass = require('sass');
module.exports = {
module: {
rules: [
{
test: /\.scss$/,
use: [
'style-loader',
'css-loader',
{
loader: 'sass-loader',
options: {
sassOptions: {
functions: {
'pow($base, $exponent)': function(base, exponent) {
return new sass.types.Number(Math.pow(base.getValue(), exponent.getValue()));
}
}
}
}
}
]
}
]
}
};
node-sass is a library that provides binding for Node.js to the Sass compiler. It allows you to natively compile .scss files to css at incredible speed. However, node-sass is deprecated in favor of Dart Sass.
postcss-loader is a tool that uses PostCSS to process CSS with JavaScript plugins. It can be used for tasks such as autoprefixing, linting, and more. While sass-loader focuses on compiling Sass, postcss-loader is more about post-processing CSS.
less-loader is similar to sass-loader but for Less, which is another preprocessor language that extends the capabilities of CSS. It's a loader for webpack that compiles Less to CSS.
stylus-loader enables webpack to compile Stylus files to CSS. Stylus is another CSS preprocessor scripting language, offering similar features to Sass/SCSS.
Use the css-loader or the raw-loader to turn it into a JS module and the mini-css-extract-plugin to extract it into a separate file. Looking for the webpack 1 loader? Check out the archive/webpack-1 branch.
npm install sass-loader node-sass webpack --save-dev
The sass-loader requires webpack as a
peerDependency
and it requires you to install either Node Sass or Dart Sass on your
own. This allows you to control the versions of all your dependencies, and to
choose which Sass implementation to use.
Chain the sass-loader with the css-loader and the style-loader to immediately apply all styles to the DOM.
npm install style-loader css-loader --save-dev
// webpack.config.js
module.exports = {
...
module: {
rules: [{
test: /\.scss$/,
use: [
"style-loader", // creates style nodes from JS strings
"css-loader", // translates CSS into CommonJS
"sass-loader" // compiles Sass to CSS, using Node Sass by default
]
}]
}
};
You can also pass options directly to Node Sass or Dart Sass:
// webpack.config.js
module.exports = {
...
module: {
rules: [{
test: /\.scss$/,
use: [{
loader: "style-loader"
}, {
loader: "css-loader"
}, {
loader: "sass-loader",
options: {
includePaths: ["absolute/path/a", "absolute/path/b"]
}
}]
}]
}
};
See the Node Sass documentation for all available Sass options.
By default the loader resolve the implementation based on your dependencies.
Just add required implementation to package.json
(node-sass
or sass
package) and install dependencies.
Example where the sass-loader
loader uses the sass
(dart-sass
) implementation:
package.json
{
"devDependencies": {
"sass-loader": "*",
"sass": "*"
}
}
Example where the sass-loader
loader uses the node-sass
implementation:
package.json
{
"devDependencies": {
"sass-loader": "*",
"node-sass": "*"
}
}
Beware the situation
when node-sass
and sass
was installed, by default the sass-loader
prefers node-sass
, to avoid this situation use the implementation
option.
The special implementation
option determines which implementation of Sass to
use. It takes either a Node Sass or a Dart Sass module. For example, to
use Dart Sass, you'd pass:
// ...
{
loader: "sass-loader",
options: {
implementation: require("sass")
}
}
// ...
Note that when using Dart Sass, synchronous compilation is twice as fast as
asynchronous compilation by default, due to the overhead of asynchronous
callbacks. To avoid this overhead, you can use the
fibers
package to call asynchronous
importers from the synchronous code path. To enable this, pass the Fiber
class
to the fiber
option:
// webpack.config.js
const Fiber = require('fibers');
module.exports = {
...
module: {
rules: [{
test: /\.scss$/,
use: [{
loader: "style-loader"
}, {
loader: "css-loader"
}, {
loader: "sass-loader",
options: {
implementation: require("sass"),
fiber: Fiber
}
}]
}]
}
};
Usually, it's recommended to extract the style sheets into a dedicated file in production using the mini-css-extract-plugin. This way your styles are not dependent on JavaScript:
const MiniCssExtractPlugin = require("mini-css-extract-plugin");
module.exports = {
...
module: {
rules: [{
test: /\.scss$/,
use: [
// fallback to style-loader in development
process.env.NODE_ENV !== 'production' ? 'style-loader' : MiniCssExtractPlugin.loader,
"css-loader",
"sass-loader"
]
}]
},
plugins: [
new MiniCssExtractPlugin({
// Options similar to the same options in webpackOptions.output
// both options are optional
filename: "[name].css",
chunkFilename: "[id].css"
})
]
};
webpack provides an advanced mechanism to resolve files. The sass-loader uses Sass's custom importer feature to pass all queries to the webpack resolving engine. Thus you can import your Sass modules from node_modules
. Just prepend them with a ~
to tell webpack that this is not a relative import:
@import "~bootstrap/dist/css/bootstrap";
It's important to only prepend it with ~
, because ~/
resolves to the home directory. webpack needs to distinguish between bootstrap
and ~bootstrap
because CSS and Sass files have no special syntax for importing relative files. Writing @import "file"
is the same as @import "./file";
url(...)
Since Sass/libsass does not provide url rewriting, all linked assets must be relative to the output.
main.scss
).More likely you will be disrupted by this second issue. It is natural to expect relative references to be resolved against the .scss
file in which they are specified (like in regular .css
files). Thankfully there are a two solutions to this problem:
$icon-font-path
. Check out this working bootstrap example.Bundling CSS with webpack has some nice advantages like referencing images and fonts with hashed urls or hot module replacement in development. In production, on the other hand, it's not a good idea to apply your style sheets depending on JS execution. Rendering may be delayed or even a FOUC might be visible. Thus it's often still better to have them as separate files in your final production build.
There are two possibilities to extract a style sheet from the bundle:
To enable CSS source maps, you'll need to pass the sourceMap
option to the sass-loader and the css-loader. Your webpack.config.js
should look like this:
module.exports = {
...
devtool: "source-map", // any "source-map"-like devtool is possible
module: {
rules: [{
test: /\.scss$/,
use: [{
loader: "style-loader", options: {
sourceMap: true
}
}, {
loader: "css-loader", options: {
sourceMap: true
}
}, {
loader: "sass-loader", options: {
sourceMap: true
}
}]
}]
}
};
If you want to edit the original Sass files inside Chrome, there's a good blog post. Checkout test/sourceMap for a running example.
If you want to prepend Sass code before the actual entry file, you can set the data
option. In this case, the sass-loader will not override the data
option but just append the entry's content. This is especially useful when some of your Sass variables depend on the environment:
{
loader: "sass-loader",
options: {
data: "$env: " + process.env.NODE_ENV + ";"
}
}
The data
option supports Function
notation:
{
loader: "sass-loader",
options: {
data: (loaderContext) => {
// More information about avalaible options https://webpack.js.org/api/loaders/
const { resourcePath, rootContext } = loaderContext;
const relativePath = path.relative(rootContext,resourcePath);
if (relativePath === "styles/foo.scss") {
return "$value: 100px;"
}
return "$value: 200px;"
}
}
}
Please note: Since you're injecting code, this will break the source mappings in your entry file. Often there's a simpler solution than this, like multiple Sass entry files.
Johannes Ewald |
Jorik Tangelder |
Kiran |
7.2.0 (2019-08-08)
sass
/scss
/css
extensions (#711) (6fc9d4e)functions
option as function (#651) (6c9654d)data
as Function
(#648) (aa64e1b)sass
and style
fields in package.json
(#647) (a8709c9)dart-sass
(ff90dd6)<a name="7.1.0"></a>
FAQs
Sass loader for webpack
The npm package sass-loader receives a total of 10,188,321 weekly downloads. As such, sass-loader popularity was classified as popular.
We found that sass-loader demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 3 open source maintainers collaborating on the project.
Did you know?
Socket for GitHub automatically highlights issues in each pull request and monitors the health of all your open source dependencies. Discover the contents of your packages and block harmful activity before you install or update your dependencies.
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